Recognition of epoxy with phage displayed peptides

The development of a general approach for non-destructive chemical and biological functionalization of epoxy could expand opportunities for both fundamental studies and creating various device platforms. Epoxy shows unique electrical, mechanical, chemical and biological compatibility and has been widely used for fabricating a variety of devices. Phage display has emerged as a powerful method for selecting peptides that possess enhanced selectivity and binding affinity toward a variety of targets. In this letter, we demonstrate for the first time a powerful yet benign approach for identifying binding motifs to epoxy via comprehensively screened phage displayed peptides. Our results show that the epoxy can be selectively recognized with peptide-displaying phages. Further, along with the development of epoxy-based microstructures; recognition of the epoxy with phage displayed peptides can be specifically localized in these microstructures. We anticipate that these results could open up exciting opportunities in the use of peptide-recognized epoxy in fundamental biochemical recognition studies, as well as in applications ranging from analytical devices, hybrid materials, surface and interface, to cell biology.     

Chemical functionalization of graphene enabled by phage displayed peptides

The development of a general approach for the nondestructive chemical and biological functionalization of graphene could expand opportunities for graphene in both fundamental studies and a variety of device platforms. Graphene is a delicate single-layer, two-dimensional network of carbon atoms whose properties can be affected by covalent modification. One method for functionalizing materials without fundamentally changing their inherent structure is using biorecognition moieties. In particular, oligopeptides are molecules containing a broad chemical diversity that can be achieved within a relatively compact size. Phage display is a dominant method for identifying peptides that possess enhanced selectivity toward a particular target. Here, we demonstrate a powerful yet benign approach for chemical functionalization of graphene via comprehensively screened phage displayed peptides. Our results show that graphene can be selectively recognized even in nanometer-defined strips. Further, modification of graphene with bifunctional peptides reveals both the ability to impart selective recognition of gold nanoparticles and the development of an ultrasensitive graphene-based TNT sensor. We anticipate that these results could open exciting opportunities in the use of graphene in fundamental biochemical recognition studies, as well as applications ranging from sensors to energy storage devices.     

Patterning Techniques for Metal Organic Frameworks

The tuneable pore size and architecture, chemical properties and functionalization make metal organic frameworks (MOFs) attractive versatile stimuli‐responsive materials. In this context, MOFs hold promise for industrial applications and a fervent research field is currently investigating MOF properties for device fabrication. Although the material properties have a crucial role, the ability to precisely locate the functional material is fundamental for device fabrication. In this progress report, advancements in the control of MOF positioning and precise localization of functional materials within MOF crystals are presented. Advantages and limitations of each reviewed technique are critically investigated, and several important gaps in the technological development for device fabrication are highlighted. Finally, promising patterning techniques are presented which are inspired by previous studies in organic and inorganic crystal patterning for the future of MOF lithography.     

New directions in mechanics

The Division of Materials Sciences and Engineering of the US Department of Energy (DOE) sponsored a workshop to identify cutting-edge research needs and opportunities, enabled by the application of theoretical and applied mechanics. The workshop also included input from biochemical, surface science, and computational disciplines, on approaching scientific issues at the nanoscale, and the linkage of atomistic-scale with nano-, meso-, and continuum-scale mechanics. This paper is a summary of the outcome of the workshop, consisting of three main sections, each put together by a team of workshop participants.Section 1 addresses research opportunities that can be realized by the application of mechanics fundamentals to the general area of self-assembly, directed self-assembly, and fluidics. Section 2 examines the role of mechanics in biological, bioinspired, and biohybrid material systems, closely relating to and complementing the material covered in Section 1. In this manner, it was made clear that mechanics plays a fundamental role in understanding the biological functions at all scales, in seeking to utilize biology and biological techniques to develop new materials and devices, and in the general area of bionanotechnology. While direct observational investigations are an essential ingredient of new discoveries and will continue to open new exciting research doors, it is the basic need for controlled experimentation and fundamentally-based modeling and computational simulations that will be truly empowered by a systematic use of the fundamentals of mechanics.Section 3 brings into focus new challenging issues in inelastic deformation and fracturing of materials that have emerged as a result of the development of nanodevices, biopolymers, and hybrid bio–abio systems.Each section begins with some introductory overview comments, and then provides illustrative examples that were presented at the workshop and which are believed to highlight the enabling research areas and, particularly, the impact that mechanics can make in enhancing the fundamental understanding that can lead to new technologies.     

Fibrillized peptide microgels for cell encapsulation and 3D cell culture

One of the advantages of materials produced by self-assembly is that in principle they can be formed in any given container to produce materials of predetermined shapes and sizes. Here, we developed a method for triggering peptide self-assembly within the aqueous phase of water-in-oil emulsions to produce spherical microgels composed of fibrillized peptides. Size control over the microgels was achieved by specification of blade type, speed, and additional shear steps in the emulsion process. Microgels constructed in this way could then be embedded within other self-assembled peptide matrices by mixing pre-formed microgels with un-assembled peptides and inducing gelation of the entire composite, offering a route towards multi-peptide materials with micron-scale domains of different peptide formulations. The gels themselves were cytocompatible, as was the microgel fabrication procedure, enabling the encapsulation of NIH 3T3 fibroblasts and C3H10T-1/2 mouse pluripotent stem cells with good viability.     

Direct micro/nano metal patterning based on two-step transfer printing of ionic metal nano-ink

We present a direct metal patterning method by a two-step transfer printing process of non-particle, ionic metal nano-ink solution. This fabrication method allows a simple direct patterning of various micro/nanoscale metallic structures. Complex structures such as multilayer line arrays, patterns along non-flat topologies, and micro/nanoscale hybrid patterns can be achieved by using this process. Also, the low temperature and pressure process conditions are compatible with the fabrication of electronic structures and devices on flexible substrates such as polyimide film and photographic papers. As an application of this process, we fabricated ZnO nanowire-based flexible UV sensors, where metal electrodes were fabricated by two-step transfer printing. In the case of ZnO nanowire sensors, highly sensitive and fast responding performances to UV illumination and good mechanical robustness against repeated bending conditions could be verified.     

Fabrication of 20 nm half-pitch gratings by corrugation-directed self-assembly

The evolution of the scaling of modern semiconductor devices is governed by the ability to create scalable high-resolution patterns on substrates. Since it is becoming increasingly difficult and expensive to extend to smaller dimensions using optical lithography, there is a great deal of interest in alternative patterning methods. The self-assembly of block copolymers in thin films, which provides periodic patterns of 10-50?nm length scales, has been recognized as a promising candidate for such patterning. To be practical, however, this approach must provide control over the orientation and lateral placement of the microdomains. We report here our discovery of the controlled alignment of the lamellar microdomains of a block copolymer containing hybrid material using topographic pre-patterns on substrates. We find that this hybrid material forms lamellae with a half-pitch of approximately 20?nm perpendicular to the lines of a surface corrugation.     

Large-scale metal oxide nanostructures on template-patterned microbowls: A simple method for growth of hierarchical structures

Hierarchical structures-metal oxide nanostructures on desired patterns of metal oxide microbowls have been successfully fabricated by combining the unique advantages of two simple techniques: template assisted self-assembly technique by which polystyrene micro/nanospheres could be readily patterned and positioned on a large scale and hot-plate technique by which metal oxide nanostructures could be easily formed. Instead of using microspheres as mask to locate the catalyst for subsequent nanostructure growth, in this work we directly employed the patterned polystyrene microspheres as a template where the metal films (Fe, Cu, Zn and Co) were deposited and the hierarchical structures were formed subsequently by a one-step low temperature (250 °C-400 °C) heating process in atmosphere. With the feasibilities like patterning, positioning and fabricating the hierarchical structures with large surface area, this simple and practical method exhibits potentials for the synthesis of a unique building block: nanostructures on the desired patterns of micro/nanobowls, for future nanoscience and nanotechnology.     

纤维材料表面图案化构筑及应用研究进展

自然界中生物体表面形形色色的图案赋予其减阻、强黏附、超疏水等多样的功能特性。受自然界的启发,研究者在平面基底表面构筑图案方面已经取得了很大研究进展。然而,纤维材料表面的图案化构筑及对纤维材料功能的影响等研究尚不深入。本文总结了目前纤维材料表面图案化的构筑方法,简述了三种"自下而上"策略的图案化形成机制;另外分析了纤维材料表面图案化对其功能的影响,展望了纤维材料表面图案化的潜在应用;最后对构筑方法、形成机制、应用领域提出了展望。本文旨在为纤维材料表面图案的构筑及功能纤维/织物更广阔的工程应用提供借鉴。     

Self-assembly: a minimalist route to the fabrication of nanomaterials

Self-assembly of molecular or nonmolecular components by non-covalent interactions offers an invaluable tool for the preparation of discrete nanostructures and extended 2D and 3D materials, which are often not accessible by any other fabrication process. In this article we summarize the most recent advances in the generation of nanomaterials such as self-assembled monolayers (SAMs) and structures formed from amphiphilic molecules, colloids, peptides, and polymers by nontemplated self-assembly either at the solid state or in solution. The current status of templated self-assembly and the use of self-assembled structures as template and for patterning other materials is also covered. A special emphasis is placed on strategies presenting either original and somehow exploratory approaches, eventually combining bottom-up and top-down methods, or that concern methods for the production of materials with potential application, e.g., in photonics, as sensors, for drug delivery and electric and magnetic devices. In all the sections, we outline self-organization and applications enabled with self-separated block copolymers.     

Electrohydrodynamic printing: a potential tool for high-resolution hydrogel/cell patterning

Electrohydrodynamic printing has gained increasing attentions to fabricate micro/nanoscale patterns in a controlled and cost-effective manner. However, most of the existing studies focus on printing tiny dried fibres, which limits its applications in high-resolution cell printing. Here we investigated the feasibility of using electrohydrodynamic printing to pattern microscale liquid filaments. Process parameters like stage moving speed and substrate resistance were optimised to stably print polyvinyl alcohol (PVA) liquid lines with the smallest line width of 37.4?μm. Complex patterns like XJTU logo with constant or variable line width were successfully printed by dynamically adjusting the moving speed. Fluorescent microparticles, with a similar diameter to living cells, were patterned in a one-by-one manner along with the PVA filaments. It is envisioned that the presented electrohydrodynamic printing method could be potentially used to high-resolution hydrogel/cell patterning for the studies of microscale cell–cell interactions or organ printing.     

Micro‐/Nanofluidics for Liquid‐Mediated Patterning of Hybrid‐Scale Material Structures

Various materials are fabricated to form specific structures/patterns at the micro‐/nanoscale, which exhibit additional functions and performance. Recent liquid‐mediated fabrication methods utilizing bottom‐up approaches benefit from micro‐/nanofluidic technologies that provide a high controllability for manipulating fluids containing various solutes, suspensions, and building blocks at the microscale and/or nanoscale. Here, the state‐of‐the‐art micro‐/nanofluidic approaches are discussed, which facilitate the liquid‐mediated patterning of various hybrid‐scale material structures, thereby showing many additional advantages in cost, labor, resolution, and throughput. Such systems are categorized here according to three representative forms defined by the degree of the free‐fluid–fluid interface: free, semiconfined, and fully confined forms. The micro‐/nanofluidic methods for each form are discussed, followed by recent examples of their applications. To close, the remaining issues and potential applications are summarized.     

Patterning of FePt for magnetic recording

Higher areal density for magnetic recording is needed to provide larger storage capacities on harddisk drives. However, as the recording bit size of traditional magnetic recording materials (such as Co/Cr) approaches 10 nm, the magnetic direction of each recording bit would become unstable at room temperature due to thermal fluctuation. To solve this problem, efforts have been made using two methods: one method is to replace the disk media with new materials possessing higher magnetic anisotropy which would lead to better thermal stability; and the second one is to employ different configurations for the recording layer. FePt with patterned media configuration is a combination of these two methods. In this paper we review some novel and interesting methods of patterning FePt for magnetic recording, including thermal patterning, self-assembly patterning, and lithography patterning.     

A General Approach for Fluid Patterning and Application in Fabricating Microdevices

Engineering the fluid interface such as the gas–liquid interface is of great significance for solvent processing applications including functional material assembly, inkjet printing, and high‐performance device fabrication. However, precisely controlling the fluid interface remains a great challenge owing to its flexibility and fluidity. Here, a general method to manipulate the fluid interface for fluid patterning using micropillars in the microchannel is reported. The principle of fluid patterning for immiscible fluid pairs including air, water, and oils is proposed. This understanding enables the preparation of programmable multiphase fluid patterns and assembly of multilayer functional materials to fabricate micro‐optoelectronic devices. This general strategy of fluid patterning provides a promising platform to study the fundamental processes occurring on the fluid interface, and benefits applications in many subjects, such as microfluidics, microbiology, chemical analysis and detection, material synthesis and assembly, device fabrication, etc.     

A triazine bridged p-phenylenevinylene polymer film for biomolecular patterning

Photo-reaction by UV irradiation of a highly fluorescent s-triazine bridged p-phenylenevinylene polymer resulted in micro and submicron fluorescent pattern because carbonyl group (C=O) was generated from vinylene group (C=C) through the photo-oxidation. This fluorescent pattern could be used for micro scale cell patterning as well as submicron scale biomolecules patterning such as proteins. When exposed to a solution containing biomolecules, the polymeric patterns were selectively coated with biomoleucles, to result in biomolecular patterns. In particular, the UV exposed area of the poly[4,6-bis(phenoxy)-2-diphenylamino-s-triazine]co(2, 5-bis(trimethylsily)-1,4-phenylenevinylene) (DTSPV) patterns was highly selective toward fluorescein isothiocyanate (FITC) conjugated-collagen. These studies provide an exciting opportunity for tissue engineering and fundamental understanding of the mechanisms of cellular adhesion, proliferation, and differentiation.     

Integrated Micro/Nanoengineered Functional Biomaterials for Cell Mechanics and Mechanobiology: A Materials Perspective

The rapid development of micro/nanoengineered functional biomaterials in the last two decades has empowered materials scientists and bioengineers to precisely control different aspects of the in vitro cell microenvironment. Following a philosophy of reductionism, many studies using synthetic functional biomaterials have revealed instructive roles of individual extracellular biophysical and biochemical cues in regulating cellular behaviors. Development of integrated micro/nanoengineered functional biomaterials to study complex and emergent biological phenomena has also thrived rapidly in recent years, revealing adaptive and integrated cellular behaviors closely relevant to human physiological and pathological conditions. Working at the interface between materials science and engineering, biology, and medicine, we are now at the beginning of a great exploration using micro/nanoengineered functional biomaterials for both fundamental biology study and clinical and biomedical applications such as regenerative medicine and drug screening. In this review, an overview of state of the art micro/nanoengineered functional biomaterials that can control precisely individual aspects of cell‐microenvironment interactions is presented and they are highlighted them as well‐controlled platforms for mechanistic studies of mechano‐sensitive and ‐responsive cellular behaviors and integrative biology research. The recent exciting trend where micro/nanoengineered biomaterials are integrated into miniaturized biological and biomimetic systems for dynamic multiparametric microenvironmental control of emergent and integrated cellular behaviors is also discussed. The impact of integrated micro/nanoengineered functional biomaterials for future in vitro studies of regenerative medicine, cell biology, as well as human development and disease models are discussed.     

A new approach to molecular devices using SAMs,LSMCD and Cat-CVD

This paper proposes a new technology for the fabrication of molecular devices using nanotechnology based on liquid and surface sciences recently developed, such as the direct patterning of solid surfaces using the difference of hydrophobic and hydrophilic properties of self-assembled mono-layers and self-assembly films of metal nanoparticles, the fine fabrication of films by the method of Liquid Source Misted Chemical Deposition, and the Langmuir–Blodgett self-assembly films. In these liquid-based technologies, various kinds of organic compounds in solutions, including biological systems, can be used as functional materials in molecular devices. In addition, it has been found that the insulating inorganic films obtained by catalytic chemical vapor deposition are quite effective in the protection of molecular devices against water and/or oxygen. We confirm, from the experimental results presented in this report, that this new approach is practically promising in future.     

Ge/Si nanowire mesoscopic Josephson junctions

The controlled growth of nanowires (NWs) with dimensions comparable to the Fermi wavelengths of the charge carriers allows fundamental investigations of quantum confinement phenomena. Here, we present studies of proximity-induced superconductivity in undoped Ge/Si core/shell NW heterostructures contacted by superconducting leads. By using a top gate electrode to modulate the carrier density in the NW, the critical supercurrent can be tuned from zero to greater than 100 nA. Furthermore, discrete sub-bands form in the NW due to confinement in the radial direction, which results in stepwise increases in the critical current as a function of gate voltage. Transport measurements on these superconductor-NW-superconductor devices reveal high-order (n = 25) resonant multiple Andreev reflections, indicating that the NW channel is smooth and the charge transport is highly coherent. The ability to create and control coherent superconducting ordered states in semiconductor-superconductor hybrid nanostructures allows for new opportunities in the study of fundamental low-dimensional superconductivity.     

Genetically engineered polypeptides for inorganics: A utility in biological materials science and engineering

Adapting molecular biology to materials science we developed peptide-based protocols for the assembly and formation of hybrid materials and systems. In this approach of generating molecular scale biomimetic materials, peptides are designed, synthesized, genetically tailored and, finally, utilized as potential molecular linkers in self-assembly, ordered organization, and fabrication of inorganics for specific technological applications. The potential areas range from molecular and nanoscale functional materials to medical fields, e.g., from diagnosis to biosensors. Here, we describe a selection of inorganic binding polypeptides via directed evolution, post-selection modifications through genetic engineering, and utility in practical applications. The selection of the inorganic binders is accomplished through combinatorial biology based peptide libraries. The diversity of applications is highlighted in three case studies. First, the molecular and nanoscale recognition of the polypeptide is presented via nanosize gold particle immobilization onto a molecular template by gold binding polypeptide. Second, we present that the alkaline phosphatase fused with multiple repeats of gold binding polypeptide can still be enzymatically active when it is immobilized onto a solid substrate. Finally, we present silica biosynthesis in aqueous environment using engineered quartz-binding peptides.     

Regular Aligned 1D Single‐Crystalline Supramolecular Arrays for Photodetectors

Solution‐processed semiconductor single‐crystal patterns possess unique advantages of large scale and low cost, leading to potential applications toward high‐performance optoelectronic devices. To integrate organic semiconductor micro/nanostructures into devices, various patterning techniques have been developed. However, previous patterning techniques suffer from trade‐offs between precision, scalability, crystallinity, and orientation. Herein, a patterning method is reported based on an asymmetric‐wettability micropillar‐structured template. Large‐scale 1D single‐crystalline supramolecular arrays with strict alignment, pure crystallographic orientation, and precise position can be obtained. The wettability difference between tops and sidewalls of micropillars gives rise to the confinement of organic solutions in discrete capillary tubes followed by dewetting and formation of capillary trailing. The capillary trailing enables unidirectional dewetting, regulated mass transport, and confined crystal growth. Owing to the high crystallinity and pure crystallographic orientation with Pt atomic chains parallel to the substrate, the photodetectors based on the 1D arrays exhibit improved responsivity. The work not only provides fundamental understanding on the patterning and crystallization of supramolecular structures but also develops a large‐scale assembly technique for patterning single‐crystalline micro/nanostructures.